<?php
require_once 'config.php';

/**
 * Write log message to file
 */
function writeLog($message, $level = 'INFO')
{
    if (!LOG_ENABLED) {
        return;
    }

    $timestamp = date('Y-m-d H:i:s');
    $logMessage = "[{$timestamp}] [{$level}] {$message}" . PHP_EOL;

    // Also log to error_log for immediate visibility
    error_log("[MAIL] {$message}");

    // Write to log file
    if (defined('LOG_FILE')) {
        file_put_contents(LOG_FILE, $logMessage, FILE_APPEND | LOCK_EX);
    }
}

/**
 * Validate email address
 */
function validateEmail($email)
{
    return preg_match(EMAIL_REGEX, $email);
}

/**
 * Sanitize input string
 */
function sanitizeInput($input)
{
    return htmlspecialchars(trim($input), ENT_QUOTES, 'UTF-8');
}

/**
 * Generate XML from form data
 */
function generateXML($data)
{
    $xml = new DOMDocument('1.0', 'UTF-8');
    $xml->formatOutput = true;

    $root = $xml->createElement('form_submission');
    $xml->appendChild($root);

    // Static data
    $static = $xml->createElement('static');
    $root->appendChild($static);

    foreach (['name', 'lastname', 'title', 'telno', 'mail', 'apparatsname', 'subject', 'semester', 'dauerapparat'] as $field) {
        if (isset($data[$field])) {
            $element = $xml->createElement($field, htmlspecialchars($data[$field]));
            $static->appendChild($element);
        }
    }

    if (!empty($data['message'])) {
        $messageEl = $xml->createElement('message', htmlspecialchars($data['message']));
        $static->appendChild($messageEl);
    }

    // Books
    if (isset($data['books']) && is_array($data['books'])) {
        $booksNode = $xml->createElement('books');
        $root->appendChild($booksNode);

        foreach ($data['books'] as $book) {
            $bookNode = $xml->createElement('book');
            $booksNode->appendChild($bookNode);

            foreach (['authorname', 'year', 'title', 'signature'] as $field) {
                $value = isset($book[$field]) ? htmlspecialchars($book[$field]) : '';
                $fieldNode = $xml->createElement($field, $value);
                $bookNode->appendChild($fieldNode);
            }
        }
    }

    return $xml->saveXML();
}

/**
 * Generate XML for ELSA form
 */
function generateELSAXML($data)
{
    $xml = new DOMDocument('1.0', 'UTF-8');
    $xml->formatOutput = true;

    $root = $xml->createElement('elsa_submission');
    $xml->appendChild($root);

    // General info
    $generalInfo = $xml->createElement('general_info');
    $root->appendChild($generalInfo);

    $generalFields = [
        'name',
        'lastname',
        'title',
        'mail',
        'subject',
        'classname',
        'usage_date_from',
        'usage_date_to',
        'availability_date'
    ];

    foreach ($generalFields as $field) {
        if (isset($data[$field])) {
            $element = $xml->createElement($field, htmlspecialchars($data[$field]));
            $generalInfo->appendChild($element);
        }
    }

    if (!empty($data['message'])) {
        $messageEl = $xml->createElement('message', htmlspecialchars($data['message']));
        $generalInfo->appendChild($messageEl);
    }

    // Media sections
    $mediaRoot = $xml->createElement('media');
    $root->appendChild($mediaRoot);

    // Add different media types (monografie, zeitschrift, herausgeber)
    $mediaTypes = [
        'monografien' => $data['monografien'] ?? [],
        'zeitschriftenartikel' => $data['zeitschriftenartikel'] ?? [],
        'herausgeberwerke' => $data['herausgeberwerke'] ?? []
    ];

    foreach ($mediaTypes as $type => $entries) {
        if (!empty($entries)) {
            $section = $xml->createElement($type);
            $mediaRoot->appendChild($section);

            foreach ($entries as $entry) {
                $entryNode = $xml->createElement('entry');
                $section->appendChild($entryNode);

                foreach ($entry as $key => $value) {
                    $fieldNode = $xml->createElement($key, htmlspecialchars($value));
                    $entryNode->appendChild($fieldNode);
                }
            }
        }
    }

    return $xml->saveXML();
}

/**
 * Send email with XML attachment
 * Uses PHP's mail() function or SMTP if configured
 */
function sendEmail($subject, $xmlContent, $toEmail = null)
{
    $to = $toEmail ?? MAIL_TO;
    $from = MAIL_FROM;

    writeLog("==========================================================");
    writeLog("Email Send Attempt");
    writeLog("From: {$from}");
    writeLog("To: {$to}");
    writeLog("Subject: {$subject}");
    writeLog("Content Length: " . strlen($xmlContent) . " bytes");

    if (!MAIL_ENABLED) {
        writeLog("MAIL SENDING DISABLED - Email not sent", 'WARNING');
        writeLog("XML Content:\n" . $xmlContent);
        writeLog("==========================================================");
        return true;
    }

    // Try using SMTP if credentials are configured
    if (SMTP_USERNAME && SMTP_PASSWORD) {
        writeLog("SMTP credentials configured, attempting SMTP send");
        $result = sendEmailSMTP($subject, $xmlContent, $to, $from);

        if ($result) {
            writeLog("Email sent successfully via SMTP", 'SUCCESS');
        } else {
            writeLog("Email sending via SMTP failed", 'ERROR');
        }

        writeLog("==========================================================");
        return $result;
    }

    // Fallback to PHP mail() only if no SMTP credentials
    writeLog("No SMTP credentials configured, using PHP mail() function");
    $headers = "From: " . $from . "\r\n";
    $headers .= "Content-Type: application/xml; charset=UTF-8\r\n";
    $headers .= "X-Mailer: PHP/" . phpversion();

    $result = mail($to, $subject, $xmlContent, $headers);

    if ($result) {
        writeLog("Email sent successfully via mail()", 'SUCCESS');
    } else {
        writeLog("Email sending via mail() failed", 'ERROR');
    }

    writeLog("==========================================================");
    return $result;
}

/**
 * Send email via SMTP using PHPMailer (if available) or native PHP sockets
 */
function sendEmailSMTP($subject, $xmlContent, $to, $from)
{
    // Try PHPMailer first if available
    if (class_exists('PHPMailer\PHPMailer\PHPMailer')) {
        writeLog("Initializing PHPMailer for SMTP send");
        writeLog("SMTP Host: " . SMTP_HOST . ":" . SMTP_PORT);
        writeLog("SMTP Encryption: " . SMTP_ENCRYPTION);
        writeLog("SMTP Username: " . SMTP_USERNAME);

        $mail = new PHPMailer\PHPMailer\PHPMailer(true);

        try {
            // Server settings
            $mail->isSMTP();
            $mail->Host = SMTP_HOST;
            $mail->SMTPAuth = true;
            $mail->Username = SMTP_USERNAME;
            $mail->Password = SMTP_PASSWORD;
            $mail->SMTPSecure = SMTP_ENCRYPTION;
            $mail->Port = SMTP_PORT;
            $mail->CharSet = 'UTF-8';

            writeLog("SMTP connection configured");

            // Recipients
            $mail->setFrom($from);
            $mail->addAddress($to);

            writeLog("Recipients configured");

            // Content - XML as body
            $mail->isHTML(false);
            $mail->Subject = $subject;
            $mail->Body = $xmlContent;
            $mail->ContentType = 'text/plain';

            writeLog("Sending email via SMTP...");
            $mail->send();

            writeLog("SMTP send() completed successfully", 'SUCCESS');
            return true;
        } catch (Exception $e) {
            writeLog("SMTP Exception: " . $e->getMessage(), 'ERROR');
            writeLog("PHPMailer ErrorInfo: " . $mail->ErrorInfo, 'ERROR');
            return false;
        }
    }

    // Helper function to read SMTP multi-line response
    $readResponse = function ($socket) {
        $response = '';
        while ($line = fgets($socket, 515)) {
            $response .= $line;
            // Check if this is the last line (code followed by space, not hyphen)
            if (preg_match('/^\d{3} /', $line)) {
                break;
            }
        }
        return $response;
    };

    // Fallback to native PHP SMTP
    writeLog("PHPMailer not available, using native PHP SMTP implementation");
    writeLog("SMTP Host: " . SMTP_HOST . ":" . SMTP_PORT);
    writeLog("SMTP Encryption: " . SMTP_ENCRYPTION);

    // Check if required transports are available
    $transports = stream_get_transports();
    writeLog("Available transports: " . implode(', ', $transports));

    if (SMTP_ENCRYPTION === 'ssl' && !in_array('ssl', $transports)) {
        writeLog("SSL transport not available. Enable OpenSSL extension in PHP.", 'ERROR');
        writeLog("Try changing SMTP_ENCRYPTION to 'tls' and SMTP_PORT to 587 in config.php", 'ERROR');
        return false;
    }

    try {
        // Build the connection string - always start with plain TCP for TLS
        if (SMTP_ENCRYPTION === 'ssl') {
            $host = 'ssl://' . SMTP_HOST;
        } else {
            $host = SMTP_HOST;
        }
        $timeout = 30;

        writeLog("Connecting to {$host}:" . SMTP_PORT);
        $smtp = @fsockopen($host, SMTP_PORT, $errno, $errstr, $timeout);

        if (!$smtp) {
            writeLog("Failed to connect: ({$errno}) {$errstr}", 'ERROR');
            return false;
        }

        writeLog("Connected successfully");

        // Read server response
        $response = $readResponse($smtp);
        writeLog("Server greeting: " . trim($response));

        // Send EHLO
        fputs($smtp, "EHLO " . SMTP_HOST . "\r\n");
        $response = $readResponse($smtp);
        writeLog("EHLO response: " . trim(str_replace("\r\n", " | ", $response)));

        // Start TLS if needed and not using SSL
        if (SMTP_ENCRYPTION === 'tls') {
            fputs($smtp, "STARTTLS\r\n");
            $response = $readResponse($smtp);
            writeLog("STARTTLS response: " . trim($response));

            if (strpos($response, '220') === 0) {
                if (in_array('tls', $transports) || in_array('ssl', $transports)) {
                    $crypto = @stream_socket_enable_crypto($smtp, true, STREAM_CRYPTO_METHOD_TLS_CLIENT);
                    if ($crypto) {
                        writeLog("TLS encryption enabled successfully");
                        fputs($smtp, "EHLO " . SMTP_HOST . "\r\n");
                        $response = $readResponse($smtp);
                        writeLog("EHLO after TLS: " . trim(str_replace("\r\n", " | ", $response)));
                    } else {
                        writeLog("Failed to enable TLS encryption", 'WARNING');
                        writeLog("Continuing without encryption (not recommended)", 'WARNING');
                    }
                } else {
                    writeLog("TLS/SSL transports not available. Enable OpenSSL extension.", 'WARNING');
                    writeLog("Continuing without encryption (not recommended)", 'WARNING');
                }
            }
        }

        // Authenticate
        fputs($smtp, "AUTH LOGIN\r\n");
        $response = $readResponse($smtp);
        writeLog("AUTH response: " . trim($response));

        fputs($smtp, base64_encode(SMTP_USERNAME) . "\r\n");
        $response = $readResponse($smtp);

        fputs($smtp, base64_encode(SMTP_PASSWORD) . "\r\n");
        $response = $readResponse($smtp);

        if (strpos($response, '235') !== 0) {
            writeLog("Authentication failed: " . trim($response), 'ERROR');
            fclose($smtp);
            return false;
        }

        writeLog("Authentication successful");

        // Send MAIL FROM
        fputs($smtp, "MAIL FROM: <{$from}>\r\n");
        $response = $readResponse($smtp);
        writeLog("MAIL FROM response: " . trim($response));

        // Send RCPT TO
        fputs($smtp, "RCPT TO: <{$to}>\r\n");
        $response = $readResponse($smtp);
        writeLog("RCPT TO response: " . trim($response));

        // Send DATA
        fputs($smtp, "DATA\r\n");
        $response = $readResponse($smtp);
        writeLog("DATA response: " . trim($response));

        // Send email headers and body
        $headers = "From: {$from}\r\n";
        $headers .= "To: {$to}\r\n";
        $headers .= "Subject: {$subject}\r\n";
        $headers .= "Content-Type: text/plain; charset=UTF-8\r\n";
        $headers .= "X-Mailer: PHP/" . phpversion() . "\r\n";
        $headers .= "\r\n";

        fputs($smtp, $headers . $xmlContent . "\r\n.\r\n");
        $response = $readResponse($smtp);
        writeLog("Message response: " . trim($response));

        // Quit
        fputs($smtp, "QUIT\r\n");
        $readResponse($smtp); // Read QUIT response
        fclose($smtp);

        if (strpos($response, '250') === 0) {
            writeLog("Email sent successfully via native SMTP", 'SUCCESS');
            return true;
        } else {
            writeLog("Email sending failed: " . trim($response), 'ERROR');
            return false;
        }

    } catch (Exception $e) {
        writeLog("Native SMTP Exception: " . $e->getMessage(), 'ERROR');
        return false;
    }
}

/**
 * Redirect to URL
 */
function redirect($url)
{
    header("Location: " . $url);
    exit;
}

/**
 * Get POST value with default
 */
function post($key, $default = '')
{
    return isset($_POST[$key]) ? sanitizeInput($_POST[$key]) : $default;
}

/**
 * Get all POST values matching a pattern (for arrays)
 */
function postArray($key)
{
    return isset($_POST[$key]) && is_array($_POST[$key]) ?
        array_map('sanitizeInput', $_POST[$key]) : [];
}